字符串转hashcode

function hashConvert(v,ext)
	local ch = 0
	local val = 0
	
	if(v) then
		for i=1,#v do
			ch = v:byte(i)
			if( ch >= 65 and ch <= 90 ) then
				ch = ch + 32
			end
			val = val*0.7 + ch  --0.7是加权
		end
	end
	val = val .. ''
	val = val:gsub("+","")
	val = val:gsub("%.","")
	

	if(ext)then
		return string.format('%s.%s',val,ext)
	else
		return string.format('%s',val)
	end
end

--test

print(hashConvert('http://192.168.1.131:8080/sns/head.jsp?id=3&width=40&height=40&type=jpeg','gif'))
print(hashConvert('http://192.168.1.131:8080/sns/head.jsp?id=5&width=40&height=40&type=jpeg','gif'))

--output
33444727508723.gif
33444733948534.gif

使用string 2 hashcode 在有些场合很方便， 比如页面图片缓存等。